<?php

if (!defined('BASEPATH'))
  exit('No direct script access allowed');
/**
 * CodeIgniter
 *
 * An open source application development framework for PHP 5.1.6 or newer
 *
 * @package		CodeIgniter
 * @author		ExpressionEngine Dev Team
 * @copyright	Copyright (c) 2008 - 2011, EllisLab, Inc.
 * @license		http://codeigniter.com/user_guide/license.html
 * @link		http://codeigniter.com
 * @since		Version 1.0
 * @filesource
 */
// ------------------------------------------------------------------------

/**
 * Security Class
 *
 * @package		CodeIgniter
 * @subpackage	Libraries
 * @category	Security
 * @author		ExpressionEngine Dev Team
 * @link		http://codeigniter.com/user_guide/libraries/security.html
 */
class CI_Security {

  /**
   * Random Hash for protecting URLs
   *
   * @var string
   * @access protected
   */
  protected $_xss_hash = '';

  /**
   * Random Hash for Cross Site Request Forgery Protection Cookie
   *
   * @var string
   * @access protected
   */
  protected $_csrf_hash = '';

  /**
   * Expiration time for Cross Site Request Forgery Protection Cookie
   * Defaults to two hours (in seconds)
   *
   * @var int
   * @access protected
   */
  protected $_csrf_expire = 7200;

  /**
   * Token name for Cross Site Request Forgery Protection Cookie
   *
   * @var string
   * @access protected
   */
  protected $_csrf_token_name = 'ci_csrf_token';

  /**
   * Cookie name for Cross Site Request Forgery Protection Cookie
   *
   * @var string
   * @access protected
   */
  protected $_csrf_cookie_name = 'ci_csrf_token';

  /**
   * List of never allowed strings
   *
   * @var array
   * @access protected
   */
  protected $_never_allowed_str = array(
      'document.cookie' => '[removed]',
      'document.write' => '[removed]',
      '.parentNode' => '[removed]',
      '.innerHTML' => '[removed]',
      'window.location' => '[removed]',
      '-moz-binding' => '[removed]',
      '<!--' => '&lt;!--',
      '-->' => '--&gt;',
      '<![CDATA[' => '&lt;![CDATA[',
      '<comment>' => '&lt;comment&gt;'
  );

  /* never allowed, regex replacement */

  /**
   * List of never allowed regex replacement
   *
   * @var array
   * @access protected
   */
  protected $_never_allowed_regex = array(
      'javascript\s*:',
      'expression\s*(\(|&\#40;)', // CSS and IE
      'vbscript\s*:', // IE, surprise!
      'Redirect\s+302',
      "([\"'])?data\s*:[^\\1]*?base64[^\\1]*?,[^\\1]*?\\1?"
  );

  /**
   * Constructor
   *
   * @return	void
   */
  public function __construct() {
    // Is CSRF protection enabled?
    if (config_item('csrf_protection') === TRUE) {
      // CSRF config
      foreach (array('csrf_expire', 'csrf_token_name', 'csrf_cookie_name') as $key) {
        if (FALSE !== ($val = config_item($key))) {
          $this->{'_' . $key} = $val;
        }
      }

      // Append application specific cookie prefix
      if (config_item('cookie_prefix')) {
        $this->_csrf_cookie_name = config_item('cookie_prefix') . $this->_csrf_cookie_name;
      }

      // Set the CSRF hash
      $this->_csrf_set_hash();
    }

    log_message('debug', "Security Class Initialized");
  }

  // --------------------------------------------------------------------

  /**
   * Verify Cross Site Request Forgery Protection
   *
   * @return	object
   */
  public function csrf_verify() {
    // If it's not a POST request we will set the CSRF cookie
    if (strtoupper($_SERVER['REQUEST_METHOD']) !== 'POST') {
      return $this->csrf_set_cookie();
    }

    // Do the tokens exist in both the _POST and _COOKIE arrays?
    if (!isset($_POST[$this->_csrf_token_name], $_COOKIE[$this->_csrf_cookie_name])) {
      $this->csrf_show_error();
    }

    // Do the tokens match?
    if ($_POST[$this->_csrf_token_name] != $_COOKIE[$this->_csrf_cookie_name]) {
      $this->csrf_show_error();
    }

    // We kill this since we're done and we don't want to
    // polute the _POST array
    unset($_POST[$this->_csrf_token_name]);

    // Nothing should last forever
    unset($_COOKIE[$this->_csrf_cookie_name]);
    $this->_csrf_set_hash();
    $this->csrf_set_cookie();

    log_message('debug', 'CSRF token verified');

    return $this;
  }

  // --------------------------------------------------------------------

  /**
   * Set Cross Site Request Forgery Protection Cookie
   *
   * @return	object
   */
  public function csrf_set_cookie() {
    $expire = time() + $this->_csrf_expire;
    $secure_cookie = (config_item('cookie_secure') === TRUE) ? 1 : 0;

    if ($secure_cookie && (empty($_SERVER['HTTPS']) OR strtolower($_SERVER['HTTPS']) === 'off')) {
      return FALSE;
    }

    setcookie($this->_csrf_cookie_name, $this->_csrf_hash, $expire, config_item('cookie_path'), config_item('cookie_domain'), $secure_cookie);

    log_message('debug', "CRSF cookie Set");

    return $this;
  }

  // --------------------------------------------------------------------

  /**
   * Show CSRF Error
   *
   * @return	void
   */
  public function csrf_show_error() {
    show_error('The action you have requested is not allowed.');
  }

  // --------------------------------------------------------------------

  /**
   * Get CSRF Hash
   *
   * Getter Method
   *
   * @return 	string 	self::_csrf_hash
   */
  public function get_csrf_hash() {
    return $this->_csrf_hash;
  }

  // --------------------------------------------------------------------

  /**
   * Get CSRF Token Name
   *
   * Getter Method
   *
   * @return 	string 	self::csrf_token_name
   */
  public function get_csrf_token_name() {
    return $this->_csrf_token_name;
  }

  // --------------------------------------------------------------------

  /**
   * XSS Clean
   *
   * Sanitizes data so that Cross Site Scripting Hacks can be
   * prevented.  This function does a fair amount of work but
   * it is extremely thorough, designed to prevent even the
   * most obscure XSS attempts.  Nothing is ever 100% foolproof,
   * of course, but I haven't been able to get anything passed
   * the filter.
   *
   * Note: This function should only be used to deal with data
   * upon submission.  It's not something that should
   * be used for general runtime processing.
   *
   * This function was based in part on some code and ideas I
   * got from Bitflux: http://channel.bitflux.ch/wiki/XSS_Prevention
   *
   * To help develop this script I used this great list of
   * vulnerabilities along with a few other hacks I've
   * harvested from examining vulnerabilities in other programs:
   * http://ha.ckers.org/xss.html
   *
   * @param	mixed	string or array
   * @param 	bool
   * @return	string
   */
  public function xss_clean($str, $is_image = FALSE) {
    /*
     * Is the string an array?
     *
     */
    if (is_array($str)) {
      while (list($key) = each($str)) {
        $str[$key] = $this->xss_clean($str[$key]);
      }

      return $str;
    }

    /*
     * Remove Invisible Characters
     */
    $str = remove_invisible_characters($str);

    // Validate Entities in URLs
    $str = $this->_validate_entities($str);

    /*
     * URL Decode
     *
     * Just in case stuff like this is submitted:
     *
     * <a href="http://%77%77%77%2E%67%6F%6F%67%6C%65%2E%63%6F%6D">Google</a>
     *
     * Note: Use rawurldecode() so it does not remove plus signs
     *
     */
    $str = rawurldecode($str);

    /*
     * Convert character entities to ASCII
     *
     * This permits our tests below to work reliably.
     * We only convert entities that are within tags since
     * these are the ones that will pose security problems.
     *
     */

    $str = preg_replace_callback("/[a-z]+=([\'\"]).*?\\1/si", array($this, '_convert_attribute'), $str);

    $str = preg_replace_callback("/<\w+.*?(?=>|<|$)/si", array($this, '_decode_entity'), $str);

    /*
     * Remove Invisible Characters Again!
     */
    $str = remove_invisible_characters($str);

    /*
     * Convert all tabs to spaces
     *
     * This prevents strings like this: ja	vascript
     * NOTE: we deal with spaces between characters later.
     * NOTE: preg_replace was found to be amazingly slow here on
     * large blocks of data, so we use str_replace.
     */

    if (strpos($str, "\t") !== FALSE) {
      $str = str_replace("\t", ' ', $str);
    }

    /*
     * Capture converted string for later comparison
     */
    $converted_string = $str;

    // Remove Strings that are never allowed
    $str = $this->_do_never_allowed($str);

    /*
     * Makes PHP tags safe
     *
     * Note: XML tags are inadvertently replaced too:
     *
     * <?xml
     *
     * But it doesn't seem to pose a problem.
     */
    if ($is_image === TRUE) {
      // Images have a tendency to have the PHP short opening and
      // closing tags every so often so we skip those and only
      // do the long opening tags.
      $str = preg_replace('/<\?(php)/i', "&lt;?\\1", $str);
    } else {
      $str = str_replace(array('<?', '?' . '>'), array('&lt;?', '?&gt;'), $str);
    }

    /*
     * Compact any exploded words
     *
     * This corrects words like:  j a v a s c r i p t
     * These words are compacted back to their correct state.
     */
    $words = array(
        'javascript', 'expression', 'vbscript', 'script', 'base64',
        'applet', 'alert', 'document', 'write', 'cookie', 'window'
    );

    foreach ($words as $word) {
      $temp = '';

      for ($i = 0, $wordlen = strlen($word); $i < $wordlen; $i++) {
        $temp .= substr($word, $i, 1) . "\s*";
      }

      // We only want to do this when it is followed by a non-word character
      // That way valid stuff like "dealer to" does not become "dealerto"
      $str = preg_replace_callback('#(' . substr($temp, 0, -3) . ')(\W)#is', array($this, '_compact_exploded_words'), $str);
    }

    /*
     * Remove disallowed Javascript in links or img tags
     * We used to do some version comparisons and use of stripos for PHP5,
     * but it is dog slow compared to these simplified non-capturing
     * preg_match(), especially if the pattern exists in the string
     */
    do {
      $original = $str;

      if (preg_match("/<a/i", $str)) {
        $str = preg_replace_callback("#<a\s+([^>]*?)(>|$)#si", array($this, '_js_link_removal'), $str);
      }

      if (preg_match("/<img/i", $str)) {
        $str = preg_replace_callback("#<img\s+([^>]*?)(\s?/?>|$)#si", array($this, '_js_img_removal'), $str);
      }

      if (preg_match("/script/i", $str) OR preg_match("/xss/i", $str)) {
        $str = preg_replace("#<(/*)(script|xss)(.*?)\>#si", '[removed]', $str);
      }
    } while ($original != $str);

    unset($original);

    // Remove evil attributes such as style, onclick and xmlns
    $str = $this->_remove_evil_attributes($str, $is_image);

    /*
     * Sanitize naughty HTML elements
     *
     * If a tag containing any of the words in the list
     * below is found, the tag gets converted to entities.
     *
     * So this: <blink>
     * Becomes: &lt;blink&gt;
     */
    $naughty = 'alert|applet|audio|basefont|base|behavior|bgsound|blink|body|embed|expression|form|frameset|frame|head|html|ilayer|iframe|input|isindex|layer|link|meta|object|plaintext|style|script|textarea|title|video|xml|xss';
    $str = preg_replace_callback('#<(/*\s*)(' . $naughty . ')([^><]*)([><]*)#is', array($this, '_sanitize_naughty_html'), $str);

    /*
     * Sanitize naughty scripting elements
     *
     * Similar to above, only instead of looking for
     * tags it looks for PHP and JavaScript commands
     * that are disallowed.  Rather than removing the
     * code, it simply converts the parenthesis to entities
     * rendering the code un-executable.
     *
     * For example:	eval('some code')
     * Becomes:		eval&#40;'some code'&#41;
     */
    $str = preg_replace('#(alert|cmd|passthru|eval|exec|expression|system|fopen|fsockopen|file|file_get_contents|readfile|unlink)(\s*)\((.*?)\)#si', "\\1\\2&#40;\\3&#41;", $str);


    // Final clean up
    // This adds a bit of extra precaution in case
    // something got through the above filters
    $str = $this->_do_never_allowed($str);

    /*
     * Images are Handled in a Special Way
     * - Essentially, we want to know that after all of the character
     * conversion is done whether any unwanted, likely XSS, code was found.
     * If not, we return TRUE, as the image is clean.
     * However, if the string post-conversion does not matched the
     * string post-removal of XSS, then it fails, as there was unwanted XSS
     * code found and removed/changed during processing.
     */

    if ($is_image === TRUE) {
      return ($str == $converted_string) ? TRUE : FALSE;
    }

    log_message('debug', "XSS Filtering completed");
    return $str;
  }

  // --------------------------------------------------------------------

  /**
   * Random Hash for protecting URLs
   *
   * @return	string
   */
  public function xss_hash() {
    if ($this->_xss_hash == '') {
      mt_srand();
      $this->_xss_hash = md5(time() + mt_rand(0, 1999999999));
    }

    return $this->_xss_hash;
  }

  // --------------------------------------------------------------------

  /**
   * HTML Entities Decode
   *
   * This function is a replacement for html_entity_decode()
   *
   * The reason we are not using html_entity_decode() by itself is because
   * while it is not technically correct to leave out the semicolon
   * at the end of an entity most browsers will still interpret the entity
   * correctly.  html_entity_decode() does not convert entities without
   * semicolons, so we are left with our own little solution here. Bummer.
   *
   * @param	string
   * @param	string
   * @return	string
   */
  public function entity_decode($str, $charset = 'UTF-8') {
    if (stristr($str, '&') === FALSE) {
      return $str;
    }

    $str = html_entity_decode($str, ENT_COMPAT, $charset);
    $str = preg_replace('~&#x(0*[0-9a-f]{2,5})~ei', 'chr(hexdec("\\1"))', $str);
    return preg_replace('~&#([0-9]{2,4})~e', 'chr(\\1)', $str);
  }

  // --------------------------------------------------------------------

  /**
   * Filename Security
   *
   * @param	string
   * @param 	bool
   * @return	string
   */
  public function sanitize_filename($str, $relative_path = FALSE) {
    $bad = array(
        "../",
        "<!--",
        "-->",
        "<",
        ">",
        "'",
        '"',
        '&',
        '$',
        '#',
        '{',
        '}',
        '[',
        ']',
        '=',
        ';',
        '?',
        "%20",
        "%22",
        "%3c", // <
        "%253c", // <
        "%3e", // >
        "%0e", // >
        "%28", // (
        "%29", // )
        "%2528", // (
        "%26", // &
        "%24", // $
        "%3f", // ?
        "%3b", // ;
        "%3d"  // =
    );

    if (!$relative_path) {
      $bad[] = './';
      $bad[] = '/';
    }

    $str = remove_invisible_characters($str, FALSE);
    return stripslashes(str_replace($bad, '', $str));
  }

  // ----------------------------------------------------------------

  /**
   * Compact Exploded Words
   *
   * Callback function for xss_clean() to remove whitespace from
   * things like j a v a s c r i p t
   *
   * @param	type
   * @return	type
   */
  protected function _compact_exploded_words($matches) {
    return preg_replace('/\s+/s', '', $matches[1]) . $matches[2];
  }

  // --------------------------------------------------------------------

  /*
   * Remove Evil HTML Attributes (like evenhandlers and style)
   *
   * It removes the evil attribute and either:
   * 	- Everything up until a space
   * 		For example, everything between the pipes:
   * 		<a |style=document.write('hello');alert('world');| class=link>
   * 	- Everything inside the quotes
   * 		For example, everything between the pipes:
   * 		<a |style="document.write('hello'); alert('world');"| class="link">
   *
   * @param string $str The string to check
   * @param boolean $is_image TRUE if this is an image
   * @return string The string with the evil attributes removed
   */
  protected function _remove_evil_attributes($str, $is_image) {
    // All javascript event handlers (e.g. onload, onclick, onmouseover), style, and xmlns
    $evil_attributes = array('on\w*', 'style', 'xmlns', 'formaction');

    if ($is_image === TRUE) {
      /*
       * Adobe Photoshop puts XML metadata into JFIF images, 
       * including namespacing, so we have to allow this for images.
       */
      unset($evil_attributes[array_search('xmlns', $evil_attributes)]);
    }

    do {
      $count = 0;
      $attribs = array();

      // find occurrences of illegal attribute strings with quotes (042 and 047 are octal quotes)
      preg_match_all('/(' . implode('|', $evil_attributes) . ')\s*=\s*(\042|\047)([^\\2]*?)(\\2)/is', $str, $matches, PREG_SET_ORDER);

      foreach ($matches as $attr) {
        $attribs[] = preg_quote($attr[0], '/');
      }

      // find occurrences of illegal attribute strings without quotes
      preg_match_all('/(' . implode('|', $evil_attributes) . ')\s*=\s*([^\s>]*)/is', $str, $matches, PREG_SET_ORDER);

      foreach ($matches as $attr) {
        $attribs[] = preg_quote($attr[0], '/');
      }

      // replace illegal attribute strings that are inside an html tag
      if (count($attribs) > 0) {
        $str = preg_replace('/(<?)(\/?[^><]+?)([^A-Za-z<>\-])(.*?)(' . implode('|', $attribs) . ')(.*?)([\s><]?)([><]*)/i', '$1$2 $4$6$7$8', $str, -1, $count);
      }
    } while ($count);

    return $str;
  }

  // --------------------------------------------------------------------

  /**
   * Sanitize Naughty HTML
   *
   * Callback function for xss_clean() to remove naughty HTML elements
   *
   * @param	array
   * @return	string
   */
  protected function _sanitize_naughty_html($matches) {
    // encode opening brace
    $str = '&lt;' . $matches[1] . $matches[2] . $matches[3];

    // encode captured opening or closing brace to prevent recursive vectors
    $str .= str_replace(array('>', '<'), array('&gt;', '&lt;'), $matches[4]);

    return $str;
  }

  // --------------------------------------------------------------------

  /**
   * JS Link Removal
   *
   * Callback function for xss_clean() to sanitize links
   * This limits the PCRE backtracks, making it more performance friendly
   * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
   * PHP 5.2+ on link-heavy strings
   *
   * @param	array
   * @return	string
   */
  protected function _js_link_removal($match) {
    return str_replace(
            $match[1], preg_replace(
                    '#href=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|data\s*:)#si', '', $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
            ), $match[0]
    );
  }

  // --------------------------------------------------------------------

  /**
   * JS Image Removal
   *
   * Callback function for xss_clean() to sanitize image tags
   * This limits the PCRE backtracks, making it more performance friendly
   * and prevents PREG_BACKTRACK_LIMIT_ERROR from being triggered in
   * PHP 5.2+ on image tag heavy strings
   *
   * @param	array
   * @return	string
   */
  protected function _js_img_removal($match) {
    return str_replace(
            $match[1], preg_replace(
                    '#src=.*?(alert\(|alert&\#40;|javascript\:|livescript\:|mocha\:|charset\=|window\.|document\.|\.cookie|<script|<xss|base64\s*,)#si', '', $this->_filter_attributes(str_replace(array('<', '>'), '', $match[1]))
            ), $match[0]
    );
  }

  // --------------------------------------------------------------------

  /**
   * Attribute Conversion
   *
   * Used as a callback for XSS Clean
   *
   * @param	array
   * @return	string
   */
  protected function _convert_attribute($match) {
    return str_replace(array('>', '<', '\\'), array('&gt;', '&lt;', '\\\\'), $match[0]);
  }

  // --------------------------------------------------------------------

  /**
   * Filter Attributes
   *
   * Filters tag attributes for consistency and safety
   *
   * @param	string
   * @return	string
   */
  protected function _filter_attributes($str) {
    $out = '';

    if (preg_match_all('#\s*[a-z\-]+\s*=\s*(\042|\047)([^\\1]*?)\\1#is', $str, $matches)) {
      foreach ($matches[0] as $match) {
        $out .= preg_replace("#/\*.*?\*/#s", '', $match);
      }
    }

    return $out;
  }

  // --------------------------------------------------------------------

  /**
   * HTML Entity Decode Callback
   *
   * Used as a callback for XSS Clean
   *
   * @param	array
   * @return	string
   */
  protected function _decode_entity($match) {
    return $this->entity_decode($match[0], strtoupper(config_item('charset')));
  }

  // --------------------------------------------------------------------

  /**
   * Validate URL entities
   *
   * Called by xss_clean()
   *
   * @param 	string
   * @return 	string
   */
  protected function _validate_entities($str) {
    /*
     * Protect GET variables in URLs
     */

    // 901119URL5918AMP18930PROTECT8198

    $str = preg_replace('|\&([a-z\_0-9\-]+)\=([a-z\_0-9\-]+)|i', $this->xss_hash() . "\\1=\\2", $str);

    /*
     * Validate standard character entities
     *
     * Add a semicolon if missing.  We do this to enable
     * the conversion of entities to ASCII later.
     *
     */
    $str = preg_replace('#(&\#?[0-9a-z]{2,})([\x00-\x20])*;?#i', "\\1;\\2", $str);

    /*
     * Validate UTF16 two byte encoding (x00)
     *
     * Just as above, adds a semicolon if missing.
     *
     */
    $str = preg_replace('#(&\#x?)([0-9A-F]+);?#i', "\\1\\2;", $str);

    /*
     * Un-Protect GET variables in URLs
     */
    $str = str_replace($this->xss_hash(), '&', $str);

    return $str;
  }

  // ----------------------------------------------------------------------

  /**
   * Do Never Allowed
   *
   * A utility function for xss_clean()
   *
   * @param 	string
   * @return 	string
   */
  protected function _do_never_allowed($str) {
    $str = str_replace(array_keys($this->_never_allowed_str), $this->_never_allowed_str, $str);

    foreach ($this->_never_allowed_regex as $regex) {
      $str = preg_replace('#' . $regex . '#is', '[removed]', $str);
    }

    return $str;
  }

  // --------------------------------------------------------------------

  /**
   * Set Cross Site Request Forgery Protection Cookie
   *
   * @return	string
   */
  protected function _csrf_set_hash() {
    if ($this->_csrf_hash == '') {
      // If the cookie exists we will use it's value.
      // We don't necessarily want to regenerate it with
      // each page load since a page could contain embedded
      // sub-pages causing this feature to fail
      if (isset($_COOKIE[$this->_csrf_cookie_name]) &&
              preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1) {
        return $this->_csrf_hash = $_COOKIE[$this->_csrf_cookie_name];
      }

      return $this->_csrf_hash = md5(uniqid(rand(), TRUE));
    }

    return $this->_csrf_hash;
  }

}

/* End of file Security.php */
/* Location: ./system/libraries/Security.php */
